A light emitting diode (LED) is a light-emitting device fabricated with a compound semiconductor, in which electric energy is converted into light through the combination of electrons and holes. An LED is a type of cold light source, and has the advantages of low power consumption, no warm up time, long service life, and fast response speed, etc. It also provides the features of small size, high impact resistance, and is suitable for mass production. Consequently, a light emitting diode is readily attuned to meet the application requirements in fabricating extremely small or array devices.
In order to expand the application range of an LED in the future, the current research focuses on improving the light-emitting brightness of the LED. In an ideal LED, after the carriers in an active region are recombined into photons and all of these photons propagate to the external environment, the light emitting efficiency of such an LED is 100%. However, not 100% of the photons generated in the active region cannot be propagated to the external environment due to various depletion mechanisms.
In order to improve the light-emitting efficiency of an LED, a patterned LED substrate, for example, an LED substrate constituted with a plurality of cones or platform structures is used to scatter the light emitted from the LED, so as to reduce the total reflection.